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September 22, 2011

Sickle Cell Disease 101

by editor

More public awareness and education about sickle cell disease, an inherited disease that affects the blood system, is critically important, said a renowned hematologist from Baylor College of Medicine and Texas Children's Hospital.

Dr. Russell E. Ware, professor of pediatrics at BCM, director of the Texas Children's Center for Global Health and director of the Texas Children's Hematology Center, offered information on the disease, what causes it, how it is treated and living with sickle cell.

What is sickle cell disease?

"It is an inherited, genetic blood disease that occurs when the shape of blood cells changes as a result of a mutation in the hemoglobin gene," Ware said.

Instead of the normal round shape, these cells curve and make a sickle-like or crescent shape that disrupts normal blood flow.

"When the cells are misshaped, they cannot flow as easily as the round, normal cells and get clogged in the blood vessels," said Ware. "The abnormal blood flow can result in a number of serious issues, including pain, pneumonia, organ damage, strokes, and life-threatening infections when the spleen gets clogged."

The spleen is what filters damage from an infection, Ware said.

Physically, you can spot the blockage, which is characterized by swelling and puffiness of the skin.

Two gene mutations vs. one

Some people carry one copy of the mutated hemoglobin gene and one normal copy. These people, who are identified as having sickle cell trait, are asymptomatic but still are carriers so they should be aware of the ability to have a child with sickle cell disease, Ware said.

"It's the person with a double dose of the bad gene that has sickle cell disease and will get very sick," said Ware. "People with sickle cell trait may not get sick themselves, but if they have a child with a person who is also a carrier, there is a 25 percent risk that their child will inherit both genes and have sickle cell disease."

Screening tests and genetic counseling are available to help people understand their risk.

Who gets sickle cell disease?

Primarily, the disease affects people of African-American, Middle Eastern or Indian descent where malaria is or was common, Ware said.

In the United States, sickle cell disease affects about 8 percent of the African-American population.

"Houston has a large sickle cell population, with over 50 new babies identified each year and 800 to 1,000 followed by BCM and Texas Children's pediatricians," said Ware.

Can it be prevented?

Because sickle cell disease is an inherited, genetic disease, it cannot be prevented, said Ware. "Our main goal is to prevent complications from the disease, and we can do that with early diagnosis, education and treatment."

All babies in the United States are screened for sickle cell at birth. If they are identified as having the disease, they are referred to pediatric sickle cell centers, where they are given early care and treatment, and parents are educated about complications and management.

How to treat complications?

"If you look at the last 100 years, we have learned a lot of information about the genetics, biochemistry and molecular biology of sickle cell disease," said Ware. "But we are only just now learning how to treat it properly."

The first reported case of sickle cell disease was in 1910, Ware noted. The focus of treatment has historically been to relieve pain and treat complications, not prevent problems or cure the disease. The regimen has included blood transfusions and, in some more severe cases, even bone marrow transplants.

In the last 20 years, however, a new approach to treatment has given promise to researchers like Ware who have pioneered work in this important area.

The treatment, called hydroxyurea, is approved by the U.S. Food and Drug Administration for adults with sickle cell but is increasingly prescribed to children. It reduces the severity of sickle cell disease by stimulating production of a form of hemoglobin present in the fetus and small infants that has the ability to block the sickling action of red blood cells.

Ware was involved in many of the early clinical trials involving this treatment and continues to conduct research on dosage and safety regarding hydroxyurea.

Living with sickle cell disease

Approximately 98 percent of sickle cell disease patients in the United States will live into adulthood, but many do not lead healthy lives, Ware said. Recurrent bouts of pain, frequent hospitalizations, and poor quality of life are common in sickle cell disease, which is why prevention of complications using hydroxyurea is now an attractive option.

Life expectancy of patients with sickle cell disease is an average of 42 in males and 48 in females.

"This is a devastating disease," said Ware. "Most adults with it have a poor quality of life. It is critical that we continue to research this disease and learn how to treat and manage it. Here in Houston, we want to offer families early treatment options to help prevent serious complications of the disease."

Ware said that globally, the problem is much more compound due to lack of screening resources and treatment.